by Professor Jayantha Kodikara, Director, ARC Smart Pavements Hub – SPARC and Dr Arooran Sounthararajah, Research Manager, ARC Smart Pavements Hub – SPARC
Roads are the largest publicly-owned infrastructure in Australia, and underpin the social, economic and cultural fabric of a nation with an annual spend of over $30 billion on road infrastructure, including the maintenance of 900,000km of road network. We are now facing significant challenges associated with road deterioration from increased traffic loads and climate change. However, the technologies of the Industry 4.0 Revolution, which integrate our physical and digital worlds, are providing opportunities for innovations in transport pavements research.
Supported by the Australian Research Council (ARC), the Smart Pavements Hub, SPARC, is the first-ever university-led collaborative research platform to address these issues in the transport pavements sector.
We established SPARC in July 2019, whose hallmark is its stakeholders’ collaborative spirit as encapsulated in the acronym ‘SPARC’ – Smart Pavements Australia Research Collaboration.
Our vision is to transform the Australian pavement industry to make pavements smarter, longer-lasting, safer, and more economical, with a lower environmental footprint.
We are developing novel testing methods that replicate field conditions for evaluating the long-term performance of granular geomaterials under repetitive heavy traffic loads and changing climatic factors.
These methods are more cost- effective, rapid and user-friendly, and will facilitate effective election of materials for road construction/rehabilitation. For example, how to modify granular geomaterials for the construction of flood-resilient pavements or how to innovate superior road materials including recycled products.
Predictive models are being developed to advance the design methods for these longer-lasting, climate-resilient pavements, such as a practical model to predict temporal variations of moisture in road pavement layers due to climatic factor changes during the service life.
Intelligent construction
‘Intelligent Construction’ broadly refers to the construction of a transport pavement, primarily using advanced sensing and automation, that achieves the target performance over its design life.
The pavement construction industry in Australia has recently increased its efforts to implement the intelligent compaction (IC) technology.
The recent international workshop on intelligent compaction organised by SPARC highlighted that countries like the US and China have implemented IC technology in practice as a mandatory requirement for contractors almost six years ahead of Australia.
In this context, our objectives are twofold: (a) to advance the current Australian practice to bring it in line with international practice [Level 3 – road map for IC by Federal
An example of SPARC’s Approach to Intelligent Construction: ‘ASSURED’ Innovation: A – affordable, S – scalable, S – sustainable, U – user-friendly, R – rapid, E – excellent, D – distinctive (after Mashelkar).
Highway Administration (FHWA), 2017], and (b) to advance IC globally to the highest level (Level 5) with SPARC innovations.
As part of these developments, we are undertaking targeted field experiments within a large test pit with dimensions of 12m (length) x 5m (width) in which an instrumented roller has been used to collect raw accelerometer data and deformation data during each roller pass for further analysis.
Inside the same pit, tests have also been performed on the compacted soil using a Nuclear Density Gauge (NDG, soil density measurement), two types of Light Weight Deflectometer (LWD, soil dynamic modulus measurement),
L-band instrument (ELBARA III, proximal measurement of soil moisture) and Ground-penetrating radar (GPR, proximal measurement of soil moisture) to evaluate the potential use of these devices for enhancing the quality management of IC.
Based on our recent theoretical developments and experimental results, we have filed a patent on the innovation of proximal measurement of pavement material density and other properties in real-time during compaction.
When this technology is fully developed, it has the potential to globally transform geomaterials compaction to the highest level (Level 5 – road map for IC by FHWA, 2017).
Field experiments in SPARC Hub test pit: (A) Roller instrumented with various sensors; (B) Ground-penetrating radar (GPR) for soil moisture measurements (proximal); (C) TDR soil moisture probes; (D) Surface roughness device; (E) L-band instrument (ELBARA III) for soil moisture measurements (proximal).
In addition, our IC research team have established two approaches for developing IC specifications with a framework for cost-benefit analysis, and we will examine them further during the upcoming IC trials in the field.
Compaction quality control
The compaction quality and uniformity of road materials can also be assessed by measuring the dynamic modulus of the material being compacted.
We have conducted a series of controlled tests in a test box (0.5m depth x 1.5m length x 1.5m width) to investigate the influence of soil density and moisture content on the dynamic modulus measured by LWD.
The data collected during this experimental program demonstrated a strong sensitivity of LWD modulus to soil moisture variation. The dynamic modulus measured by LWD on the compacted soil layer showed a progressive increase during the soil dry-back process by virtue of the increase in soil suction and the reduction in degree of saturation (DoS).
Further analysis is undertaken based on unsaturated soil dynamics to establish a correction factor for variations in the soil dynamic modulus due to the changes in moisture content.
Pavement dry-back experiment: variations of soil suction, moisture content and modulus were monitored continuously in a compacted soil layer (400mm thick) respectively using tensiometers, soil moisture sensors and a light weight deflectometer (LWD) during the dry-back process.
Asphalt IC trials
For asphalt compaction, we have identified the limitations of IC technology and current compaction testing methods in using them during asphalt pavement compaction.
The effects of asphalt mat temperature and underlying support on Intelligent Compaction Measurement Values (ICMVs) measured by IC rollers are the main causes of the poor correlation between asphalt ICMVs and spot density measurements.
We have proposed potential ways to overcome these limitations and establish performance-based specifications for QA/QC of asphalt compaction.
The proposed correction methods for asphalt ICMVs have been examined in a small- scale asphalt testbed construction using an IC roller.
Asphalt IC trial at ARRB’s ALF site at Dandenong: (A) Double drum roller instrumented with accelerometers, IR thermometer, GPS, and onboard control box and operator interface; (B) Thermocouples installed at various depths within the asphalt layer; (C) Non-nuclear density gauge (NNDG) measurement on the hot asphalt layer.
Sparc intelligent compaction analyser
Further, we are developing a hardware/software kit known as SPARC Intelligent Compaction Analyser (SICA), for intelligent construction of transport pavements.
SICA facilitates visualisation of multiple ICMVs that include Compaction Meter Value (CMV, Caterpillar & Hamm), Compaction Control Value (CCV, Sakai), Vibratory Modulus (Evib, BOMAG & Dynapac), Roller Integrated Stiffness (kb, Ammann) alongside the proximal density of the material being compacted.
It may be noted that the existing IC kits in the market only allow visualisation of a limited number of ICMVs (in many cases, only a single ICMV is plotted).
SICA will provide versatility to retrofit any existing conventional roller, flexibility to incorporate corrections for different ICMV indicators and facilitate customising to construction specifications in line with the Industry 4.0 revolution.
SICA is configured to be integrable with the existing post- processing software such as Veta to view and analyse the collected IC data. The experiences gained through using SICA in real IC projects will pave the way to develop robust and data-oriented specifications for IC to be used by the Australian pavement construction industry.
Authors
Professor Jayantha Kodikara, Professor and Director, ARC Industrial Transformation Research Hub (ITRH) – SPARC, Dept. of Civil Engineering, Monash University, Clayton Campus, VIC 3800, Australia. Get in touch at jayantha.kodikara@monash.edu.
Dr Arooran Sounthararajah, Research Manager, ARC Industrial Transformation Research Hub (ITRH) – SPARC, Dept. of Civil Engineering, Monash University, Clayton Campus, VIC 3800, Australia. Get in touch at arooran.sounthararajah@monash.edu.
For more information, please visit sparchub.org.au.
Thanks for this excellent work . Much needed for the construction of unbound pavements with thin bituminous seals.